There are many patents that relate generally to the subject of application of heat and/or cooling to a patient to promote healing, reduce swelling, and the like. Many of these disclosures relate to complex apparatus; see U.S. Pat. Nos. 4,844,072 to French et al, 5,077,980 to Weber, and 5,080,089 to Mason et al. Other complex systems for regulating body temperature in adverse environments (i.e., for both heating and/or cooling) are shown in U.S. Pat. Nos. 3,670,518 to Esposito, 2,648,325 to Siple, and 5,201,365 to Siegel. Other patents generally relevant to the subject matter of the present invention include U.S. Pat. Nos. 3,612,059 to Ersek; 5,072,875 to Zacoi; 5,165,400 to Berke; 4,459,468 to Bailey; 4,367,743 to Gregory; 301,931 to Smith et al; 4,856,294 to Scaringe et al; 4,981,135 to Hardy; 5,143,064 to Cochran, and 2,911,974 to Spence.
The prior art applicable to this invention also includes U.S. Pat. Nos. 3,871,381 to Roslonski and 5,170,783 to Smith. Of these, Roslonski discloses a "cold compress device" wherein an inflatable compress is connected to a controllable source of pressurized refrigerant. As the refrigerant is controllably released into the compress, it expands, effectively cooling the compress. The fact that elevated pressures are involved limits the use of the Roslonski device.
More particularly, postoperative patients commonly benefit from chilling body joints and the like, to reduce swelling and pain, and to speed their healing. In accordance with present trends toward outpatient and self-care wherever possible, it would be desirable to provide a simple and cost-effective system for convenient cooling of body joints that would be suitable for in-home, outpatient use by a patient without assistance, as well as for hospital use.
U.S. Pat. No. 5,170,783 to Smith, referred to above, discloses a "cryotherapeutic procedure" and related apparatus that has utility for thus chilling a bone joint or the like, but has numerous shortcomings. The Smith system comprises a reservoir of chilled fluid (e.g., ice water) that is elevated with respect to a compress fitting around the joint to be chilled. A tube carries the fluid to the compress, chilling the joint; the pressure head controlled by the difference in height between the reservoir and compress controls the pressure in the compress, which may be further controlled by a flow-controlling valve in the supply line.
Accordingly, in use of the Smith device, the compress is initially filled with cold water, and is pressurized responsive to the pressure head, as above. Over time, the water in the compress will be warmed responsive to heat transfer from the limb being cooled, such that the temperature in the compress rises gradually. When it is desired to replenish the cold water in the compress, it must be drained and refilled manually. In practice, this requires frequent attention and is a substantial inconvenience.
It would be possible, of course, to provide a small pump driven by an electric motor or the like for recirculating the warm fluid from the Smith compress to the reservoir. Various of the patents referred to above show such externally-powered positively-driven personal cooling systems providing recirculation of the coolant. However, this would inevitably complicate the device, would require power cords and the like, and would increase its cost.